1. Field of the Invention
Embodiments of the present invention relate to electric tools and, more specifically, to electric tools such as electric cutting tools and electric drilling tools that use battery packs as power sources (DC power sources).
2. Description of the Related Art
Japanese Laid-Open Patent Publication Nos. 2010-201598, 2008-18498 and 61-8289 disclose techniques relating to a cutting tool that uses a battery pack as the power source. The cutting tool may be a portable circular saw that includes a base for contacting with the upper surface of a workpiece, and a tool main body supported on the upper side of the base. The tool main body may include a circular saw blade, an electric motor for rotating the saw blade, and a handle portion that can be grasped by the user for moving the portable circular saw. As disclosed in the above-mentioned publications, the battery pack may be repeatedly used by being recharged by a charger separately prepared. In general, this kind of electric tool may be held by hand while being used. Therefore, various improvements have been made for this type of electric tool for securing visibility of the workpiece to be machined, securing operability during the machining operation, and configuring the size to be small.
The electric tool may include a controller that can automatically stop the supply of the electric power to the motor under a predetermined condition. For example, the controller may forcibly stop the supply of the electric power to the motor when the battery pack is in an over-discharge state or when the motor is in an over-current state. Such over-discharge state and over-current state are factors leading to a short service life of the battery pack. Thus, in an electric tool to which a battery pack is mounted, it is desirable to avoid the over-discharge state and the over-current state as much as possible. In the case that the controller is used for a brushless motor, the controller must have a relatively large size. On the other hand, due to its nature as a controller, the controller may generate heat. Therefore, it is desirable that the electric tool is designed by taking the cooling of the controller into consideration.
Therefore, there has been a need in the art for securing the cooling of a controller of an electric tool while achieving a reduction in the size of the electric tool.